Testing Metallicity Indicators at Z ~ 1.4 with the Gravitationally Lensed Galaxy CASSOWARY 20*

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Testing Metallicity Indicators at Z ~ 1.4 with the Gravitationally Lensed Galaxy CASSOWARY 20*

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Title: Testing Metallicity Indicators at Z ~ 1.4 with the Gravitationally Lensed Galaxy CASSOWARY 20*
Author(s):
James, Bethan L.;
Pettini, Max;
Christensen, Lise;
Auger, Matthew W.;
Becker, George D.;
King, Lindsay J. (UT Dallas);
Quider, Anna M.;
Shapley, Alice E.;
Steidel, Charles C.
Item Type: Article
Keywords: Show Keywords
Abstract: We present X-shooter observations of CASSOWARY 20 (CSWA 20), a star-forming (SFR ~ 6 M⊙ yr⁻¹) galaxy at z = 1.433, magnified by a factor of 11.5 by the gravitational lensing produced by a massive foreground galaxy at z = 0.741. We analysed the integrated physical properties of the H II regions of CSWA 20 using temperature- and density-sensitive emission lines. We find the abundance of oxygen to be ~1/7 of solar, while carbon is ~50 times less abundant than in the Sun. The unusually low C/O ratio may be an indication of a particularly rapid time-scale of chemical enrichment. The wide wavelength coverage of X-shooter gives us access to five different methods for determining the metallicity of CSWA 20, three based on emission lines from H II regions and two on absorption features formed in the atmospheres of massive stars. All five estimates are in agreement, within the factor of ~2 uncertainty of each method. The interstellar medium (ISM) of CSWA 20 only partially covers the star-forming region as viewed from our direction; in particular, absorption lines from neutrals and first ions are exceptionally weak. We find evidence for large-scale outflows of the ISM with speeds of up 750 km s⁻¹, similar to the values measured in other high-z galaxies sustaining much higher rates of star formation.
Publisher: Oxford University Press
ISSN: 0035-8711
Persistent Link: http://hdl.handle.net/10735.1/4081
http://dx.doi.org/10.1093/mnras/stu287
Terms of Use: ©2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society

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